**Core Concept**
The first clinical sign of Vitamin A deficiency is related to the role of retinol in maintaining the integrity of the cornea and the visual pathway. Vitamin A is essential for the production of rhodopsin, a pigment necessary for night vision. A deficiency in Vitamin A can lead to impaired visual function.

**Why the Correct Answer is Right**
The correct answer is related to the fact that Vitamin A deficiency primarily affects the retina, leading to impaired night vision. This is due to the decreased production of rhodopsin, which is essential for the adaptation of the eye to low light conditions. The lack of rhodopsin results in impaired visual function, making it difficult for individuals with Vitamin A deficiency to see in the dark. This condition is often referred to as night blindness.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because night blindness is a specific symptom of Vitamin A deficiency, and it is not a general term for all symptoms of the condition.
* **Option B:** This option is incorrect because conjunctival xerosis, or dryness of the conjunctiva, is a symptom of Vitamin A deficiency, but it is not the first clinical sign.
* **Option C:** This option is incorrect because Bitot's spots are a symptom of Vitamin A deficiency, but they are not the first clinical sign of the condition.

**Clinical Pearl / High-Yield Fact**
It is essential to note that Vitamin A deficiency can have significant consequences, including impaired vision, increased risk of infections, and even death. Therefore, early detection and treatment of Vitamin A deficiency are crucial.

**Correct Answer: C. Night blindness**